US2287386A - Ignition control - Google Patents

Description

June 23, 1942.

l. E. MCCABE IGNITION CONTROL Filed my 7, 1940 2 Sheets-v-Sheet 1 INVENTOR.

ATroRNEY.

June 23, 1942. x. E. MccABE IGNITION CONTRL Filed Hay 7, 1940 2 Sheets-Sheet 2 'Patented' June 23, 1942 UNITED STATES PATENT OFFICE IGNITION CONTROL Ira E. McCabe, Chicagmlll.

Application May 7, 1940, Serial No. 333,815 claims. `(ci. 15s-2s) This invention relates to improvements in electrically operated and controlled fluid fuel burning mechanisms for heating systems and more particularly to an ignition device employed therein.

It is desirable each time the system calls for heat and the burner motor delivers fuel to the combustion chamber that an ignition device will be operative to ignite the fuel and prevent deli ery of unignited fuel to flood the combustion chamber before ignition takes place.

It is an object of this invention to provide, as a part of the control mechanism, an electrical ignition device so constructed that each time the motor switch is closed the ignition device will be operative, continue in operation for a predetermined period, then become inoperative, and as soon as the motor switch is opened during the normal operation of the system or at any other time, such as caused by a power failure; even momentarily, the ignition device will be placed in position to operate on the next closing of the motor switch.

itis a further object of this invention to so construct the ignition'switch and actuating parts forming the improved ignition device that the closing of the motor switch will close a circu-it y Figure l is a View in front elevation showing f a preferred form of this invention, illustrating a commercial type of iiuid fuel burner heating system in diagram with a wiring diagram of the circuits employed therein.

Figure 2 is a fragmentary enlarged detail view in front elevation or the improved ignition device control and the operating parts thereof, in the position assumed when the burner mechanism is idle.

Figure 3 is a view in end elevation looking totorswitch and motor switch operator. p

Figure 4 is a similar view in end elevation, looking toward the right end of Figure 2.

Figure 5 is a view similar to Figure 2, illustrating the position assumed by the parts when the motor switch is closed and the ignition switch still closed when the burner mechanism is starting.

Figure 6 is a view similar to Figure 5, illustrating the .position assumed by the ignition switch at the end of the ignition period.

Figure 7 is a view similar to Figure 6, illustrating the position assumed by the parts after the ignition period has been completed and the y .from the panel P. The furnaceor heater F is shown with an oil burner of commercial form operatively installed therewith. The oil burner includes a burner motor BM, an ignition transformer IT, connected with the electrodes E arranged in front of the burner nozzle. The operation of the burner motor is controlled by a room thermostat RT of commercial form. The motor switch M is opened and closed by a commercial form of repulsion relay including a stationary primarycoil PC and a movable secondaryv coil SC. The winding of the primary coil PC is always connected in circuit with the commercial line L and L'.A The commercial line L yis connected to wire I, which preferably conducts Vthe commercial current through a boiler control BC to the safety switch S- and from there through the binding post 2 to one end of the winding of the primary coil PC. The other end of the winding of the coil PC is connected by wire k 3 through binding post 4 to the other commercial line L. The current of the commercial line passing through wire I divides at binding post 2 and part of it passes by way of wire 5 through the motor switch-M and through binding post 6 and through burnerV motor BM, and from thence by way of wire 'I to binding post 4 and from thence by way of wire 3 to commercial line L. The windings of the secondary coil SC are ,connected by wires 8 through the room thermostat RT and through binding post 9, through the ward the left end of Figure 2, omitting the moelectrical resistance heater RH, lforming a part of the commercial device for operating the safety switch S, and through binding post I0. When the system calls for heat and the circuit is closed through the room thermostat the secondary coll is energized and is repelled from the primary coil PC to close the motor switch M. When the room thermostat opens thecircuit the coil is deenergized andits weight falls to rest upon the primary coil PC and opens the motor circuit. This is a commercial construction and need not be explained in detail. In order to prevent the heating of the resistance heater RH to open the safety switch S, a shunt circuit is provided by wires II passing through a control switch preferably in the form illustrated in this applicants prior Patent No. 2,162,098 of June 13, 1939, responsive to the presence or absence of a'lame at the burner, which, when combustion is established, acts through the Wires II to shunt out the heater RH.

The construction so far described relaes to that part of a commercial system of oil burner controls for the normal starting and stopping of the burner in response to the room thermostat, as well as the stopping of the burner by a safety apparatus upon the absence of the burner flame. In such systems where ignition means are employed -for igniting the burner, igniion control devices are generally employedwhich render the ignition means operative when placing the o`il burner in operation and thereafter render the ignition means inoperative after the burner is operating. This invention relates to such ignition controldevices and will now be described.

The ignition switch I is connected from commercial line L, through the motor switch M, to the ignition transformer IT by the wire I2 leading from the binding post 6 to which the wire from the motor switch'is connected. The current, after passingA through wire I2 and the ignition switch I, then passes by the way of wires I3, through a resistance heater I4, to the ignition transformer IT. The current passing through the ignition transformer is connected by wire I5 to wire 1 which returns the current from the motor to the commercial liney L. Whenthe motor switch M is closed to establish the motor circuit,

a circuit is also set up through the resistance 'heater I4, ignition switch I, and ignition transformer. The resistance heater I4 is operatively associated with a strip of bimetallic metal I6, one end of which is fixed to a bracket I'I formed integral with a face plate I8, then bent around the ing, move in the opposite direction. This move- .a

ment of the free end I9 of the bimetallic strip I6 is employed to open the ignition switch I.

The ignition switch I is preferably a mercury Iube 'switch which is mounted upon a rotatable carrier plate so that when the switch is tilted in one direction it will close the circuit therethrough and when tilted in lche opposite direction will break the circuit therethrough. This type of mercury tube switch is a commercial article and need not be explained in detail.A The carrier plate 20 is rotatably mounted upon the pivot 2l extending between the front plate I8 and the base plate 22, as shown in Figures 1 and 4. The base plate 22, as illustrated in Figure 4, is spaced apart from the panel P by spacing studs 23, which also serve to support core 24 of the repulsion relay including the coils PCand SC. The pivoted ignition switch carrier plate 20 is extended above a bracket extension 25 therefrom, supporting the ignition switch I and is provided with an arcuate toothed segment 26 concentric with the pivot 2l andis also provided with a tooth 21 extending from the side opposite the ignition switch I below the center of a radius exiending from the pivot 2l to the arcuate toothed segment 26. An ignition switch latch is mounted on a pivot 28 extending between the base plate 22'and the front plate I8 at the left and above the ignition switch I.

The ignition switch latch is provided with a portion extending to the right of its pivot and above the toothed segment 26 and terminates in a pawl 29 adapted to ride over the teeth of the segment 26 when the carrier plate 20 isrotated to the right upon its pivot 2I and to engage in lthe teeth and prevent counter-revolution. The

latch also includes a portion 30 depending from the end adjacent the pawl 29 and extends below the ignition switch I. The weight of the latch will normally cause the pawl 29 to enga-ge the toothed segment 26. In order to lift the latch so that the pawl 29 is out of engagement with the teeth of the segment 2B to allow the ignition switch to return to its normal closed position when the secondary coil has been de-energized, a latch release in the form of an arm 3| is preferably secured to the upper side of the coil SC and is so arranged in relation to the free end of the depending portion 30 of the latch that when the secondary coil is de-energized'and has fallen to rest upon the primary coil, as shown in Figures 1 and 2, the latch release 3| has engaged the lower end of the depending portion 30 to ro-` tate the latch about its pivot 28 to lift the pawl 29 out of engagement with the toothed segment 26. When the room thermostat calls vfor heat and the secondary coil is repelled to close the motor switch M the latch release 3I is carried out of engagement with the depending portion 30 of the latch so that the latch may rotate about its pivot 28 to engage the pawl 29 with the Vtoothed segment 26, as shown in Figures 5, 6

and 7.

The ignition switch I is so mounted on the switch carrier plate 20 that when free to rotate the mercury tube -switch will assume its closed position to allow the ignition circuit to pass therethrough when established. In orderl to rotate the switch carrier plate 20 about its pivot to tilt the ignition switch I to its open position, an actuating plate 32 is-mounted on a pivot 33 soldered or otherwise secured to the extremity of the free end I9 of the bimetallic member I6 responsive to the presence or absence of heat in the electrical resistance heater I4. This actuating plate 32 is provided on its under side with a toothed rack 34 adapted to be engaged by the tooth 21 on the carrier plate 20. A slot 35 is provided in the actuator plate above the rack 34, the upper portion of which is adapted to be engaged by stud 36 mounted upon the depending portion 30 of the latch, extending through the slot 35 and so arranged that when the latch has been lifted to free the pawl 29 from the toothed segment 26 of the carrier plate,

the stud 36 will lift the actuating plate 32 to free the rack 34 from engagement with the tooth 2'I upon the switch carrier plate and when the latch release 3I has released the-latch to allow the pawl 29 to engage the toothed segment 26, the actuator, plate 32 will be allowed to rotate about its pivot 33 so that the rack 34 will be in engagement with the tooth 2'I upon the switch carrier plate. The teeth of the rack 34 are'so constructed that, when the energization of the heater I4 is established the free end I9 of the bimetallic member is caused to move toward the right, to engage the teeth of the rack 34 with the tooth 21 to rotate the carrier plate 2U to tilt the ignition switch to the open position, as shown in Figures 6 and 7.

By this construction, it is seen that when the heating system is idle the room thermostat is in the open position as the temperature of the room is satisfied. The parts of this ignition control assume the position shown in Figures l and 2. The latch release 3l has rotated the latch about its pivot 28 to lift the pawl 29 out of engagement with the toothed segment 26 upon the switch carrier plate 20 and at the same time, lifted the actuator plate 32 by the stud 36 to lift the rack 34 free of the tooth 21 whereby the weight of the mercury tube switch I rotates the switch carrier plate 20 to support the ignition switch in its closed position.

With the boiler control switch BC and safety switch S closed, a circuit is established to the primary coil PC from the commercial line. When the temperature in the room containing the room thermostat descends below the predetermined degree for which the thermostat is set, the thermostat closes and establishes the circuit through the wire 8 from one winding of the secondary coil through the safety switch resistance heater RH to the other winding of the secondary coil SC. rThis circuit not only energizes the resistance heater RH of the safety switch, but also energizes the secondary coil, causing it to be repelled from the primary coil to assume the position in starting the burner, as illustrated in Figure 5. The repulsion of the secondary coil SC removes the iatch release 3i to allow the' latch to rotate about its pivot 28 and engage its pawl Z9 with the right end portion oi the toothed segment 26 upon the carrier plate 20, and at the same time, drops the actuator plate 32 to engage its rack 34 with the tooth 21 upon the carrier plate 20. The repulsion of the coil SC also rotates the mercury tube switch M in the motor circuit to its closed position whereby a circuit is established by the wire from the binding post 2 through the motor switch M, binding post 6, burner motor BM, and wire 1 to binding post 4 and the operation of the motor is initiated, At the same time, a circuit is established by the wire I2 from the binding post 5 through the normally closed ignition switch I and by wire I3 through the electrical resistance element I4 to the ignition transformer IT and from thence through wire I5 to wire 1 to complete the circuit. It is therefore seen that the closing of the motor switch energizes the ignition transformer to cause the igniter electrodes E to produce a spark, at the same time that the operation of the burner motor BM is initiated, to ignite the fluid fuel passing through the nozzle by operation of the motor BM. During the normal operation of the commercial system illustrated in Figure l, the production of a ame in the burner nozzle will shunt the resistance heater RH of the safety switch.

The passage of the current through wires I2 and I3 which energize the electricall resistance heating element I4 causes the free end I9 of the bimetallic strip I6 to move toward the right, and as the rack 34 is in engagement with the tooth 21 this movement will rotate the carrier plate 20 to tilt the ignition switch to the open position; as shown in Figure 6 of the drawings. As the electrical resistance heater I4 is in series with the ignition circuit, as soon as the ignition switch has been tilted to the open positionthe circuit through the :heating element I4 is opened and as it cools the bimetallic strip I6 will cause its free end I9 to move to the left and as shown in Figure 7, the teeth of the rack 34 upon the actuator plate 32 will wipe over the tooth 21 of the carrier plate 28which plate 2li is held in its rotated position by engagement of the pawl 29 of the latch with the toothed segment 26 thereon. When the free end I9 of the bimetallic strip has returned the actuator plate 32 to the idle position shown in Figure 2, the ignition switch I is maintained in 'its open position, as shown in Figure 7.

- During the normal operation of the heating system when the temperature of the room has been satisfied, the room thermostat opens and immediately the repulsion relay becomes deenergized and the secondary coil SC thereof drops to rest upon the stationary primary coil PC and causes the. latch release 3l to engage the depending portion of the latch to lift the pawl 29 out of engagement with the toothed segment 26 of the switch carrier plate and as this lifting 0f the latch causes the stud 36 thereon to engage the under edge of the slot 35 in the actuator plate 32 to lift the rack 34 out of engagement with. the tooth 2? upon the carrier plate, the carrier plate is then free to rotate and tilt the ignition switch I to its closed position.

The duration of the ignition period, that is, the time between the initiai closing of the circuit through the ignition switch until the movement of the end i 9 of the bimetallic member I6 through the toothed rack 34 of the actua-tor plate 32 in engagement with the tooth 21 on vthe carrier plate rotates the carrier plate to open the ignition switch, may be adjusted by the knurled headed set screw 31 threaded through a post 38 between the iront plate I6 and the base plate 22 in line with the left end 39 of the segmental portion 26 oi the carrier plate 20 which will determine the position of the plate 20 when the ignition switch I is in its closed position.

It is therefore apparent that the ignition device described herein, provides for the immediate restoration of the ignition switch I to closed position with each opening of the motor switch M- independent and irrespective of' the operative condition of the bimetallic actuator 32, at the time, since the action of the latch release 36 while disengaging the pawl 29 from the teeth 26 also removes the actuator from operative engagement with the tooth 21 mounted upon the ignition switch carrier. Thus, the ignition switch always returns to its starting position from which a full period of ignition begins upon reclosing the motor switch.

It is further seen that there is no delay required to allow the bimetal to cool to its cold position before operation can be resumed. Even with the maximum ignition period which may be provided with the adjustment 31, bimetal may be `used which will provide a much greater range of movement than is utilized to openthe ignition switch so that there may be a series of interruptions followed by a reclosing of the motor circuit by switch M, with the assurance that not less than a full period of ignition will be provided each time.

Of course, should the opening and closing of the motor switch be so frequent and numerous that the full movement of the bimetal has been obtained by continuous heating, the ignition trol switch, electrically operated means for actul ating said switch to open and closed position, an ignition circuit including an electrical ignition device therein, a switch normally urged to closed position connected in the ignition circuit energized through said burner control switch for the electrical ignition device, a normally inactive electro-thermal actuator rendered operative upon the closure of both the burner control and ignition switches, means rendered active by the electrical operated means upon closing the burner control switch to establish an operative connection between the electro-thermal actuator and closed ignition switch to cause the opening of the ignition switch by the thermal actuator after a predetermined movement of theV actuator and thereafter hold the ignition switch open while the electro-thermal actuatorreturns to normal inactive position, said-means, upon deenergization of the electrically operated means to open the main switch, adapted to remove the operative connection between the thermal actuator and ignition switch and release the ignition switch from its held open position to allow its immediate return to its normally closed position irrespective of the condition of the electro-thermal actuator.

2. A control for the electrical ignition means 'employed with electrically operated iluid fuel burners, a burner motor circuit including a control switch, electrically operated means for actuating movable after a predetermined degree of movement to position said switch in open position said switch connected in the ignition circuit energized through said burner control switch for the electrical ignition device, an electro-thermal element having an electric heater in the ignition circuit controlled by the ignition switch, means, actuated by the thermal element, movable into and out of operative engagement -with the ignition switch operating means, a latch actuated by the electrically operated means upon closing the burner control switch to allow said thermal actuated means to move into operative engagement with the ignition switch means tocause the opening of the ignition switch by the thermal element when heated and to hold the ignition switch when opened while the thermal element cools, said latch upon 'deenergization of the electrically operated means to open the burner control switch adapted to remove the thermally actuated means from operative engagement with the ignition switch operating means and release said switch from its held open position to allow its immediate return to its normally closed position.

3. An ignition control for an electrically operated and controllediluid fuel burning mechanism including a burner motor circuit, a switch in the burner motor circuit, electrically actuated means for opening and closing the motor switch and an ignition circuit having an electrical ignition device therein, a switch in the ignition circuit Ior the electrical ignitiondevice connected in parallel to the motor circuit, said ignition switch normally urged to closed position, a thermal strip, an electrical resistance heater element controlled by the ignition switch energized upon the closing of the motor circuit associated with the thermal stripadapted to warp in response to lheat and impart movement to its free end, an actuator plate pivotally mounted upon the said free end adapted to be reciprocated thereby, a pivoting carrier plate mounting the ignition switch, a tooth upon the carrier plate and a rack upon the actuator plate adapted to engage the tooth to rotate the carrier plate to open the ignition circuit upon movement of the actuator plate in one direction and as the strip cools t0 wipe over the tooth when traveling in the opposite direction.

4. 'I'he structure of claim 3, wherein said carrier plate is provided with a toothed segment upon itsl upper surface and wherein a plvoted latch is provided having a pawl adapted to ride over the toothed segment as the carrier plate moves the ignition switch to open position and engages the segment to prevent countermovement, said latch provided with a depending arm adapted to be engaged by a latch release when the motor switch opens to release the engagement of the latch with the carrier plate to allow he return of the ignition switch to open posiion.

5. An ignition control for an electrically operated and controlled fluid fuel burning mechanism including a burner motor circuit, a switch in the burner motor circuit, electrically actuated means for opening and closing the motor switch and an ignition circuit having an electrical ignition device therein, a switch in the ignition circuit for the electrical ignition device connected in parallel to the motor circuit, said ignition switch normally urged to closed position, a pivoted carrier plate mounting said ignition switch, an electrical resistance heater element connected in series with the ignition switch, a thermal strip secured at one end and responsive to the heating element to impart movement to the free end of the strip, an actuator plate carried by the free end of the strip, a tooth upon the side of the carrier plate, a rack upon the actuator plate arranged to engage the tooth to rotate the carrier plate upon movement in one direction and to wipe over the tooth upon reverse movement, a toothed segment upon the carrier plate, a pivoted latch having a pawl adapted to ride over the toothed segment as the plate is rotated to open the ignition switchI and engage the toothed segment to prevent counter-rotation, a latch release operatively associated with the motor switch adapted to engage the'latch when the .motor switch opens to release the carrier plate to return the ignition switch to closed position, a slot in the actuator plate and a stud on the latch received therein and adapted to engage the actuator plate when the latch is released to lift the lactuator plate out of engagement with the tooth .on the carrier plate.

ma E. MCCABE,

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